1. Field of the Invention
This invention is directed to an aqueous silicone coating composition for providing lubricity to substrates, such as suture needles, hypodermic needles or razor blades. The invention is also directed to a method of coating such substrates with an aqueous silicone composition and the coated surgical needles produced thereby.
2. Related Background Art
Silicone compositions have been used to coat, and thus provide lubricity to, various articles of manufacture. U.S. Pat/ No. 3,574,673 describes coating articles having fine cutting edges with copolymers of methylsiloxane and aminoalkylsiloxane. This reference discloses applying the copolymer through the use of an inert solvent carrier, such as isopropyl alcohol, toluene or benzene.
U.S. Pat. Nos. 4,720,521 and 4,806,430 disclose the use of a film-forming composition, comprising three different reactive siloxane polymers and a non-reactive lubricating siloxane polymer, that is applied and used on a substrate, such as a hypodermic needle, to increase the lubricity of that substrate. The film-forming siloxane compositions of these references are applied to the desired substrate by using an inert, organic solvent carrier, such as a chlorofluorocarbon (e.g., those materials known by the trademark Freon.RTM..)
European Patent Application Publication No. 494,648 describes a coated surgical needle prepared by applying to a surgical needle a curable silicone composition comprising an aminoalkyl siloxane and at least one other copolymerizable siloxane. A mixture of dimethyl cyclosiloxane and dimethoxysilyldimethylamino-ethylaminopropyl silicone polymer is disclosed as the preferred silicone composition. This reference teaches that the silicone composition is applied to the surgical needle as a solution in an organic solvent such as hexane, trichlorotrifluoroethane, 1,1,1-trichloroethane or mineral spirits.
European Patent Application Publication No. 500,229 discloses a method of coating a suture needle by depositing a silicone solution containing a silicone and a solvent on the needle. The solution-coated needle is subsequently exposed to a gas atmosphere to form a layer of silicon adjacent and adhered to the outer surface of the needle. The remaining unadhered silicon is removed from the needle with a solvent. The reference teaches polydimethylsiloxane as an exemplary silicone, while acetone, a Freon.RTM. chlorofluorocarbon, trichloroethane or methylene chloride are mentioned as exemplary solvents.
Prior to this time, silicon coating solutions used to impart lubricity to various articles of manufacture, such as suture needles and razor blades, have required the presence of an inert organic solvent carrier. However, organic fluorocarbon solvents employed in many of these compositions are known to be detrimental to the atmospheric ozone layer and their use is being phased out by worldwide treaty. Additionally, other organic solvents used in known coasting compositions are either toxic or environmentally hazardous. The organic solvents used in known silicone coating compositions also increase the costs of those compositions, particularly since they are a large percentage of the compositions.
It is an object of this invention to provide a novel aqueous silicone coating composition which can be used to effectively lubricate substrates, such as suture needles, without the substantial use of organic solvent carriers.
It is a further object of this invention to provide a method for lubricating a substrate by applying an aqueous silicone coating composition to the substrate and thereafter curing the silicone thereon.
It is also an object of this invention to provide a suture needle having excellent lubricating properties prepared by the process of coating the needle with an aqueous silicone coating composition and curing the silicone thereon.